Safety in Excavations

Safety factors for excavations at construction sites

1. Excavations & Trenching
1PPT-011-01

2. 2
Definitions
•"Excavation" means any:
• 1. Man-made cut
• 2. Cavity
• 3. Trench
• 4. Depression in an earth surface, formed by
earth removal.

3. 3
Definitions
•Confined space is a space that, by design and/or
configuration has:
• 1. Limited openings for entry and exit
• 2. Unfavorable natural ventilation
• 3. May contain or produce hazardous substances
• 4. Is not intended for continuous employee
occupancy.

4. Objectives
•Highlight the hazards of working in a
excavation.
•How to protect employees from cave-ins.
•Factors that pose a hazard to employees
working in excavations.
•The role of a competent person at an
excavation site.

5. General Requirements
•Before any excavation actually begins, the employer must
determine the estimated location of utility installations:
Sewer, telephone, fuel, electric, water lines, or any other
under ground installations that may be encountered during
digging.
•A competent person will inspect, on a daily basis, excavations
and adjacent areas for possible cave-ins, failure of protective
systems and equipment, hazardous atmospheres, or other
hazardous conditions.
•Takes prompt corrective measures to eliminate hazards.
•Adequate protective systems will be utilized to protect
employees. This can be accomplished through: Sloping,
Shoring, or Shielding.

6. General Requirements
•Workers must be supplied with and wear any PPE
deemed necessary to assure their protection.
•Mechanical excavators and power tools should not be
used within 0.5 m
•If a trench is 4 feet or deeper, stairways, ramps, or
ladders will be used.
•The employees must not have to travel any more than
25 feet to reach the stairways, ramps, or ladders.
•4 feet and more trenches – Toxic and hazardous
atmosphere will be tested daily.

7. Definitions
•Excavation – a man-made cut, cavity, trench or
depression formed by earth removal.
•Trench – a narrow excavation. The depth is greater
than the width, but not wider than 15 feet.
•Shield - A structure able to withstand a cave-in and
protect employees (also called box).
•Shoring - A structure that supports the sides of an
excavation and protects against cave-ins.
•Sloping - A technique that employs a specific angle of
incline on the sides of the excavation. The angle
varies based on assessment of impacting site factors.

8. Definitions
Cave-ins are perhaps the most feared trenching hazard.
But other potentially fatal hazards exist including:
•Asphyxiation due to lack of oxygen in a confined
space
•Inhalation of toxic fumes, drowning, etc.
•Electrocution or explosions can occur when workers
contact underground utilities.

9. Excavation Hazards
–Surface encumbrances
–Utilities
–Access/Egress
–Vehicle traffic
–Falling loads
–Mobile equipment
–Hazardous atmospheres
–Water accumulation
–Adjacent structures
–Loose rock or soil
–Falls
–Cave-in

11. Definitions
Cave-In:
•Means the separation of a
mass of soil or rock material
from the side of an
excavation, or the loss of soil
from under a trench shield or
support system, and its
sudden movement into the
excavation, either by falling
or sliding, in sufficient
quantity so that it could
entrap, bury, or otherwise
injure or immobilize a person.

12. Anatomy of a Cave - In:
There is usually no warning before a cave-inThere is usually no warning before a cave-in

13. Causes of Cave – Ins

14. Causes of Cave – Ins
When water is present
in an excavation it is
extremely hazardous
to enter. Also no head
protection

15. Causes of Cave – Ins
Note: telephone pole
adjacent to
excavation, not
supported / removed

16. Injury and Death
•Excavating is one of the most
hazardous construction operations
•Most accidents occur in trenches 5-
15 feet deep
•There is usually no warning before a
cave-in
16

17. Protection of Employees
•Employees should be protected from cave-ins by using an
adequately designed protective system.
•Protective systems must be able to resist all expected loads to the
system.
17

18. Protect Employees Exposed to Potential Cave-ins
•Slope or bench the sides of the
excavation.
•Support the sides of the
excavation.
•Place a shield between the side of
the excavation and the work area.
18

19. Requirements for Protective Systems
19
A well-designed protective system Correct
design of:
- Sloping and benching systems
- Support systems
- Shield systems
- Other protective systems
+
Appropriate handling of materials and equipment
+
Attention to correct installation and removal
=
Protection of employees at excavations.

20. Design of Protective Systems
The employer shall select and construct :
→Slopes and configurations of sloping and
benching systems.
→Support systems, shield systems and other
protective systems.
•Shield - Can be permanent or portable. Also known as
trench box or trench shield.
•Shoring - Such as metal hydraulic, mechanical or timber
shoring system that supports the sides.
•Sloping - Formed sides of an excavation that are inclined
away from the excavation.
20

21. 21
Requirements for protective systems
•Protection of employees in
excavations
•Design of sloping and
benching systems
•Design of support systems,
shield systems, and other
protective systems
Materials and equipment
Installation and removal

22. 22
Protection of employees in excavations
•(1) Each employee in an excavation shall be protected from
cave-ins by an adequate protective system designed in
accordance with paragraph (b) or (c) of this section except
when:
–(i) Excavations are made entirely in stable rock; or
–(ii) Excavations are less than 5 feet (1.52 m) in depth and
examination of the ground by a competent person
provides no indication of a potential cave-in.

23. 23
Cave-in Hazard
This excavation
has inadequate
support posts and
egress access.
Inadequate protective system
PPT-011-01

24. Inadequate Protective System
•
24
This worker is in a
trench, with no
protective system,
that is neither sloped
nor benched, and has
no means of egress.
PPT-011-01

25. Factors Involved in Designing a Protective
System
•Soil classification
•Depth of cut
•Water content of soil
•Changes due to weather and
climate
•Other operations in the vicinity
25PPT-011-01

26. Shoring
•General
• Provides a framework in which to work
• Uses walls, cross braces and uprights
• Supports excavation walls
• Must know soil type
• Must know depth and width of excavation
26

27. Trench Shield
A trench shield
(also called a
trench box) was
built around this
work area.
27PPT-011-01

28. Hydraulic Trench Support
•Using hydraulic jacks, the
operator can easily drop the
system into the hole.
•Once in place, hydraulic
pressure is increased to keep
the forms in place.
•Trench pins are installed in
case of hydraulic failure.
28PPT-011-01

29. Materials and Equipment
•Equipment used for protective
systems must not have damage or
defects that impair function.
•If equipment is damaged, a
competent person must examine it
to see if it is suitable for continued
use.
•If not suitable, remove it from
service until a professional
engineer approves it for use.
29
Trench Box
PPT-011-01

30. Protection from Vehicles
•Install barricades
•Hand/mechanical signals
•Stop logs
•Grade soil away from
excavation
•Fence or barricade
trenches left overnight
30

31. 31
Hazardous Conditions
They should not be
working under this crane.
The weight and vibration
of the crane makes this a
very hazardous condition.
PPT-011-01

32. Spoil Piles
•Don’t place spoils within two feet
from edge of excavation.
•Measure from nearest part of the
spoil to the excavation edge.
•Place spoils so rainwater runs away
from the excavation.
•Place spoil well away from the
excavation.
32

33. 33
Other Excavation Hazards
•Water accumulation
•Oxygen deficiency
•Mobile equipment
•Access/egress
•Toxic fumes
•Falls
PPT-011-01

34. Access
The ladder should extend
3 feet above the
excavation

35. Access
These two
ladders which
are lashed
together are not
an adequate
means of egress
The ladder
should extend 3
rungs above the
top of the
excavation

36. Ladder to be 1 Meter Above Wall

37. Excavation Protection Systems
•There are three basic protective systems used
in excavations and trenches:
1.Sloping and Benching Systems
1.Shoring Systems
2.Shielding Systems

38. Simple Sloping

39. Benching

40. Shoring Systems
Support system for
trench faces used to
prevent movement of
soil, underground
utilities, foundations.
There are two basic
types of shoring,
timber and aluminum
hydraulic.

41. Shoring Systems

42. Timber Shoring Installations

43. Hydraulic Shoring

44. Pneumatic Shoring

45. Shielding Systems
A- Trench Boxes:
The space between
the outside of the
trench box and the
face of the trench
should be small as
possible, and
backfilled to prevent
lateral movement of
the box.

46. Excavation Inspections
•Daily Inspections of ALL excavations by Competent
Person at Start of shift, or as needed, following
rainstorms or other hazard-increasing event:
•Possible cave-ins
•Protective system failure
•Water accumulation
•Hazardous atmospheres
Competent person has authority to remove workers from
the excavation

47. Inadequate Protective System
This excavation
has inadequate
support posts
and egress
access.

48. Inadequate Protective System
This worker is in a
trench with no
protective system,
that is not sloped
or benched and has
no means of egress.

49. Hazardous Condition
The weight and
vibrations of the
machinery above
make this a very
hazardous condition.
They should not be
working under any
machinery.

50. Hydraulic Trench Support
Using hydraulic jacks the
operator can easily drop
the system into the hole.
Once in place, hydraulic
pressure is increased to
keep the forms in place.
Trench pins are installed
in case of hydraulic
failure.

51. Hazardous Atmosphere
Test excavations more
than 4 feet before an
employee enters the
excavation for:
Oxygen deficiency.
High combustible gas
concentration.
High levels of other
hazardous substances.

52. 52
Means of egress
•Means of egress from trench excavations:
• 1. A stairway, ladder, ramp or other safe
means of egress shall be located in trench
excavations that are 4 feet (1.22 mm) or
more in depth.
• 2. A means of egress should require no
more than 25 feet (7.62 m) of lateral travel
for any employee to reach.

53. 53
Inspections
•Daily inspections of excavations, the adjacent
areas, and protective systems shall be made by a
competent person for evidence of a situation that
could result in:
• 1. Possible cave-ins
• 2. Indications of failure of protective systems
• 3. Hazardous atmospheres
• 4. Other hazardous conditions.

54. 54
Inspections Cont.
•An inspection shall be conducted by the competent
person:
• 1. Prior to the start of work and as needed
throughout the shift.
• 2. After every rainstorm or other hazard
increasing occurrence.
• 3. These inspections are only required when
employee exposure can be reasonably anticipated.

55. Safety considerations
•Excavation is one of the most hazardous
types of work in the construction industry
•Accidents result from inadequate
planning
•Build safety into pre-bid planning
• Plan safety into the job. Consider:
–Traffic
–Nearness of structures and their conditions
–Soil

56. Safety considerations
•Plan safety into the job. Consider:
–Surface and ground water
–Water table
–Overhead/ underground utilities
–Weather

57. Jobsite safety and health programs
•Establish and maintain a safety and health
program for the worksite
•Provide adequate systematic policies,
procedures, practices
•Recognize job-related safety/health hazards

58. Jobsite safety and health programs
•Safety and health programs should reflect the
unique characteristics of the jobsite
•Proper implementation depends on
cooperation among:
–supervisors
–employee groups
–individual employees

59. Locating utilities
•Employers must determine the estimated
locations of utility installations
•Contact utility companies before starting
excavation
•Utility owners must attempt to find exact
location of utilities
•Proceed with caution if the exact location of
utilities cannot be found
•Use safe and acceptable means to locate exact
locations of installations

60. Safety starts at the surface
•Surface encumbrances that create hazards must be
removed/supported
•Wear warning vests when near traffic
•Employees must be trained to operate heavy
equipment
•Stay away from loads being handled by
lifting/digging equipment

61. Safety starts at the surface
•Warn mobile equipment operators about
the edge of the excavation site
•Keep the grade away from the excavation
site
• Stay away from vehicles being
loaded/unloaded

62. Employee access/egress from excavations
•Ramps must be designed by a competent person
•Ramps must be structurally sound and not create a
tripping hazard
•Use surface treatments on ramps to prevent slipping
•Trenches 4 or more feet deep need a safe means of
egress
–Stairway
–Ladder
–Ramps
•Means of egress must be fixed and secure

63. Employee access/egress from excavations
•Means of egress must be within 25 feet of
workers
•Ladders must extend a minimum of 36 inches
above the landing
•Use metal ladders with caution around utilities